As a teenager (that's my excuse anyway), I carried a 55g by the brace and busted it. I did fill it with water before I realized that the brace was important - had over an inch of flex in the glass - scary crazy. I put a clamp accross the top -> was a 12" threaded bar (like a big bolt), put that accross the top, and screwed some metal plates over that (then painted black) - believe it or not, I had it like that for 15 years before trading it.
But a new top sounds like a better idea.